The present invention relates to packaging technology, and more specifically, to an electromagnetic interference shield package and methods for providing and using the electromagnetic interference shield package.
Electromagnetic interference (EMI) is the impairment of a wanted electromagnetic signal by an electromagnetic disturbance. Each electronic component operates using a flow of charge carriers, the flow inducing a surrounding electromagnetic field. This surrounding electromagnetic field may cause sufficient noise within surrounding electronic components that the performance of the surrounding electromagnetic components is degraded. EMI is a particular problem in cellular phones in which an antenna emits radio frequencies (RF) which could affect the other circuitry operating in the phone. In order to isolate an electronic component from EMI, EMI shielding has been recently developed.
Lin (U.S. Pat. No. 5,436,203) discusses an EMI shielded device. FIG. 1 is a cross-sectional view of a similar EMI shielded device. In FIG. 1, an electrically insulating encapsulant 38 mechanically protects a semiconductor die 32. The electrically insulating encapsulant 38 is constrained by a dam structure 40 so as not to encapsulate electrically conductive reference pads 18. Reference pads 18 are electrically connected to the reference plane 22 by electrically conductive vias 20. An electrically conductive encapsulant 42 is dispensed over the first encapsulant and is in contact with the reference pads 18. The electrically conductive encapsulant 42 is constrained by a second dam structure 44.
The shielding of device 32 requires the fabrication of two separate dam structures 40 and 44. This requires two separate process steps, one step for the deposition of each dam structure 40 and 44. Furthermore, the size of the package 30 is much larger than the size of the device 32 because a dam structure 40 must surround device 32 while a separate dam structure 44 surrounds the dam structure 40. This double dam structure results in a large footprint of package 30 on a printed circuit board.
It is desirable to reduce the number of process steps in packaging a semiconductor device. It is also desirable to reduce the package size relative to the device size.
In accordance with the present invention, a package for a device is described. The package includes a substrate having a common voltage plane and a mounting region. The device is mounted to the mounting region. An electrically conductive dam structure is disposed on the upper surface of the substrate. The electrically conductive dam structure is electrically coupled to the common voltage plane and circumscribes a perimeter of the mounting region. An electrically insulating encapsulant at least partially fills a pocket defined by the substrate and the electrically conductive dam structure. The electrically insulating encapsulant contacts the electrically conductive dam structure. An electrically conductive encapsulant overlies the electrically insulating encapsulant and is coupled to the electrically conductive dam structure.
The package in accordance with the present invention shields the device from EMI such as radio frequency (xe2x80x9cRFxe2x80x9d) interference using only one dam structure. Since a double dam structure of the prior art uses an additional dam structure surrounding a primary dam structure, the package of the present invention is substantially smaller (e.g., by 10 to 20 percent or more) compared to the double dam structure package of the prior art.
In accordance with the present invention, a method of packaging a device is described as follows. The method includes providing a substrate having a common voltage plane and a mounting region. The device is mounted to the mounting region. The method includes providing an electrically conductive dam structure disposed on the upper surface of the substrate. The electrically conductive dam structure is electrically coupled to the common voltage plane and circumscribes a perimeter of the mounting region. The method includes providing an electrically insulating encapsulant which at least partially fills a pocket defined by the substrate and the electrically conductive dam structure. The electrically insulating encapsulant contacts the electrically conductive dam structure. The method includes providing an electrically conductive encapsulant that overlies the electrically insulating encapsulant and which is coupled to the electrically conductive dam structure.
The method of fabricating in accordance with the present invention results in an EMI shield device in which only one dam structure is fabricated. The number of dam structures in the conventional double dam structure package may be two. Each dam structure deposition requires a separate process step.
Therefore, the method of the present invention reduces the number of steps required to fabricate an EMI shield device.
In accordance with the present invention, a method of using a package includes applying a common voltage to the common voltage plane. A context for the common voltage plane is as follows. The device is mounted to a mounting region of the substrate. An electrically conductive dam structure is disposed on the surface of the substrate around a periphery of the mounting region. The electrically conductive dam structure is electrically coupled to the common voltage plane. The electrically insulating encapsulant at least partially fills a pocket defined by the substrate and the electrically conductive dam structure. An electrically conductive encapsulant overlies the electrically insulating encapsulant. The electrically conductive encapsulant being electrically coupled to the electrically conductive dam structure.
The method of using the device in accordance with the present invention allows for the use of a device that is EMI shielded and is smaller than conventional EMI shielded devices.